Hollow grinders are commonly used for sharpening tool blades, and typically include a tool rest for maintaining a desired orientation of the blade relative to the grinding wheel. This orientation determines the grinding or bevel angle with respect to the longitudinal axis of the tool blade.
The tool rest is typically adjustable with two or more degrees of freedom to facilitate adjustment of the height and attitude of the tool blade, while maintaining a sufficiently small air gap between the tool rest and the grinding wheel to prevent operator injury. Simultaneously achieving a desired bevel-angle and air-gap can be both difficult and time consuming, and most hollow-grinding machines have no mechanism for determining the bevel angle that will be achieved with a given setting of the tool rest. Furthermore, the bevel angle varies with the radius of the grinding wheel, which decreases with use. My prior U.S. Pat. No. 6,381,862, issued on May 7, 2002, discloses a bevel angle indicator utilizing a novel tool rest support mechanism that maintains a prescribed and coordinated height-attitude relationship of the tool rest with respect to the grinding wheel axis, and a pointer that can be adjusted according to the radius of the grinding wheel. However, it would be advantageous from a cost standpoint to utilize a more conventional tool rest support mechanism, and in many applications, a digital readout of the bevel angle is desired.